87 300TD head/engine repair

[96 E300D]

Hi All,
My dad has an 87 300TD that started overheating, took it to a shop that pulled off the head which showed a couple of visible cracks. At least one piston top looks as though something got caught in the combustion chamber and took a pounding. I think the mileage is close to 200K, brakes and front end were just gone through. Is it worth putting the money into a new/rebuilt head and possibly rebuilding the block as well? What are some good avenues to pursue to find decent prices for the parts if it is worth it? What about a complete long block?
Many Thanks,
Matt